Aristide Economopoulos/The Star-Ledger Congressman John Adler is undecided about voting on the health reform bill.WASHINGTON — U.S. Rep. John Adler Thursday delivered a kick in the gut to President Obama by announcing his opposition to health care reform, defecting at the last minute after playing coy for months.

It was not the kind of move that endears a congressman to his colleagues. In an institution that rewards seniority and party loyalty, it is hard to imagine how Adler, the freshman who bolted, will dig out of this hole.

Thursday, he presented himself as a man of conscience, concerned only about rising health care costs, and not considering his position in the party for one second.

"I don’t care about that," he said. "I care about doing the right thing for the district and the country."

Fine. But for those who see politicians as something a little less pure, here’s the low-down.

Adler is barely hanging on to this job. He squeaked into Congress in 2008 during the Obama landslide in New Jersey, and is the first Democrat to serve the mostly conservative 3rd District in a century.

And now Jon Runyan has arrived to challenge him. If you don’t know that name, then you’re not from Adler’s district, which lies mostly in Philadelphia Eagles country.

Runyan was one of the NFL’s premier offensive lineman for years. There are respected people in Philadelphia who would pay money to shine his shoes. He is a hero. Adler is not.

Add this to the mix: The health reform is about as popular in Adler’s district as a flaming skin rash.

Adler has held several public meetings on the topic, and every time he’s hit by a tidal wave of opposition. A forum in Toms River on Saturday that was supposed to be on tax reform turned into a pep rally against health reform.

"It’s overwhelmingly against the bill," Adler says. "We’re in a different world than we were two years ago. One in 10 people who wants to work in my district is without a job. And that fundamentally changes people’s perspective."

It’s always tough to gauge politicians, to figure out when they are sincere and when they are playing for votes. You can’t know for sure because you can’t peer into their souls.

But you have to ask anyway. And that’s where Adler really blew it yesterday by saying something that is just about impossible to believe, at least for someone who follows Jersey. Asked how this vote will affect the contest with Runyan, Adler acted as if it had never crossed his mind.

"I haven’t thought about that," he said. "The politics will work itself out."

Whatever his motive, Adler’s central objection to the reform is reasonable. He wants tighter cost controls. Many Democrats who support the bill feel the same way.

Yes, he goes overboard when he says this bill does nothing to control costs. It establishes exchanges to sharpen competition among insurers. It reduces Medicare payments. Pilot programs will explore new payment methods to cut costs. It imposes a tax on high-cost plans that have been weakened but not killed. The Congressional Budget Office said yesterday the bill will cut the federal deficit by $1.3 trillion over the next two decades.

But the bigger point is that Adler is missing the significance of this moment. If the reform fails now, the cause of providing health care for all Americans could become radioactive for another decade.

Rep. Bill Pascrell, a fellow Democrat, says he’s been trying to drill that point into Adler’s head for months. "I agree with him on the bill," Pascrell says. "But we need to move forward."

When Social Security passed, it excluded millions of African-American farm workers. That was fixed later. And that’s how politics works. Coalitions are built, and they lumber forward slowly.

Adler doesn’t seem to get that. Last night, he said that if the bill fails, Obama will present a new improved reform that still attempts to provide universal coverage.

"I think he’ll come back next week and do a better bill," he said. Sure. After the man gets poked in the eye with a sharp stick, his first reaction will be to line up for another jab. Again it’s hard to tell if Adler really believes this stuff, or is trying to soften the hard edges of this move.

In any case, a vote is expected in the House on Sunday. Yesterday, Speaker Nancy Pelosi was still scrambling for every vote, and Obama canceled a foreign trip so he could help. This will be close.

Adler’s hope, naive or not, is that he’ll emerge not as an outcast, but as a man of sturdy principles. "A lot of people here are respected for voting their consciences," he says.